The invention relates to an apparatus for motion-compensated picture signal interpolation, such as a field rate doubling apparatus for obtaining a flicker-free display of picture signals, or an interlace-to-progressive scan converter. The invention further relates to a receiver for television signals including such an apparatus.
Motion-compensated picture signal interpolation is known in the art. Although experiments have shown that images obtained by motion-compensated picture signal interpolation techniques can be better than those obtained by other picture signal interpolation techniques, motion-compensated picture signal interpolation is not yet widely used because of the complexity of the hardware for the motion vector estimation which is necessary to furnish motion vectors, and for the motion-compensated interpolation itself. More specifically, current implementations of motion vector estimation and compensation apparatuses require several expensive field memories. For example, U.S. Pat. No. 4,731,651 describes a field number converter in which a first field memory is used for motion vector estimation, while second and third field memories are used for motion-compensated interpolation by means of the estimated vectors.
The article "Aspekte der Normwandlung von HDTV in bestehende Fernsehstandards" in the periodical Fernseh- und Kino-Technik, Vol. 42, No. 4/1988, pp. 177-184, describes an apparatus for converting a picture signal having 60 interlaced fields per second into a picture signal having 50 interlaced fields per second. In this article, it is proposed to estimate motion vectors on the basis of input and output signals of an image memory, i.e. a two-field memory, and to perform a motion-compensated position interpolation on the basis of the input and output signals of the same two-field memory by means of the estimated motion vectors. However, the article states that this motion-compensated position interpolation is to be realized later when optimal and feasible motion detection and motion-compensation methods have been developed.